Striated flagellar roots occur associated with the basal apparatus of flagellated or ciliated eukaryotic cells and have been observed in association with centrioles and primary cilia. Striated flagellar roots are contractile organelles. We have recently demonstrated that striated flagellar roots are composed in large part of a calcium-binding 20,000 mol. wt. contractile phosphoprotein. This protein shares many features of the parvalbumin/troponin c/calmodulin superfamily of calcium-binding proteins. We present preliminary findings which suggest that antigenic homologs of the striated flagellar root protein occur associated with the centrioles and mitotic spindle poles of diverse organisms, including mammalian cells. Our ultrastructural studies indicate that the fibrous material and their condensations (pericentriolar satellites) of mammalian centrosomes is composed at least in part of antigenic homologs of striated flagellar roots. These findings have led to the proposal that striated flagellar root homologs respresent 'primitive' motile systems that are simple in composition and undergoe contraction directly in response to calcium binding. If these ideas are correct they have important implications for our understanding of eukaryotic cell structure and contractile function. We propose to characterize the antigenic homologs of the striated flagellar root protein in mammalian cells. We propose to generate a library of monoclonal antibodies and to use these in epitope mapping, immunofluorescent and immunoelectron microscopic studies of striated flagellar root homologs in mammalian cells. In addition we will characterize calcium-binding to the protein and its proteolytic fragments and study the characteristics of flagellar root protein phosphorylation.